1. Field of the Invention
The present invention relates, in general, to variable capacity rotary compressors and, more particularly, to a variable capacity rotary compressor designed to reduce an electric power loss thereof.
2. Description of the Related Art
As is well known to those skilled in the art, variable capacity rotary compressors are devices which may be used in refrigeration systems, such as air conditioners or refrigerators operated with refrigerant continuously and repeatedly flowing through a refrigeration cycle which includes compression-condensation-expansion-evaporation, to compress the refrigerant to a high pressure, prior to discharging the compressed refrigerant to a condenser.
A conventional variable capacity rotary compressor includes a drive unit and a compressing unit, both of which being installed in a hermetic casing. The drive unit generates a rotating force, and the compressing unit compresses the refrigerant by using the rotating force of the drive unit. A rotating shaft is axially arranged in the hermetic casing such that the rotating shaft rotates by the rotating force of the drive unit, and transmits the rotating force to the compressing unit.
The compressing unit includes a compressing chamber, and a roller rotatably set in the compressing chamber. The roller of the compressing unit eccentrically rotates in the compressing chamber by the rotating force of the rotating shaft, thus compressing the refrigerant in the compressing chamber.
The conventional variable capacity rotary compressor includes a refrigerant inlet pipe which feeds the refrigerant into the compressing chamber while allowing the rotary compressor to compress the refrigerant while being controlled in a capacity thereof. An inlet pipe control valve is provided at the refrigerant inlet pipe to open or to close the refrigerant inlet pipe, as desired. When the inlet pipe control valve closes the refrigerant inlet pipe, an introduction of the refrigerant into the compressing chamber is stopped, so that the capacity of the rotary compressor is variably controlled.
However, when the drive unit is operated without the refrigerant being fed into the compressing chamber, the roller of the compressing unit rotates in the compressing chamber while compressing no refrigerant, such that electric power is undesirably wasted by the conventional variable capacity rotary compressor. Further, a negative pressure is generated in the compressing chamber to disturb a rotation of the rotating shaft, so that the negative pressure increases a loss of electric power of the conventional variable capacity rotary compressor.